Non collapse stemming of casing subjected to explosive effects

ABSTRACT

Tubular casing is installed along a formation interval through which open communication is to be preserved or established in proximity to an explosive device, particularly, a nuclear explosive. The casing is then filled, i.e., is stemmed with a fluidic agent having dilatant properties. When subjected to the severe stresses product by detonation of the explosive the dilatant agent is transitorally transformed into a rigid incompressible form which prevents buckling and crushing of the casing. Upon dimination of the stress the agent returns to a fluidic form which may drain or otherwise fugitively depart from the casing providing open communication therethrough.

C United States Patent [151 3,707,188

Heckman 1 51 Dec. 26, 1972 s41 NON COLLAPSE STEMMING 0F 3,620,301 11/1971 Nichols ..166/247 CASING SUB ECTED TO EXPLOSIVE J FOREIGN PATENTS OR APPLICATIONS EFFECTS Inventor: Richard A. Heckman Castro v y 1,279,994 I 1/1961 France "166/247 C l'f.

a 1 Primary Examiner-Joseph H. McGlynn [73] Assignee: The United States of America as Assistant E i r-Lawrenc J Sta-ab rePresented y the Ulliied Sums Atzorney-Roland A. Anderson Atomic Energy Commission 221 Filed: April 27, 1971 [571 ABSTRACT [21] AppL 137,922 7 Tubular easing is installed along a fermation interval through which open commumcat1on 1s to be preserved or established in proximity to an explosive device, par- U.S. CL ticularly a nuclear explosive. The casing is the filled lift. Cl. Le. is stemmed a agent having dilatant [58] Field of Search ..107/21, 21.4, 21.6, 23; properties, wh bj t d t th vere stresses 165/247, 299, 63 product by detonation of the explosive the dilatant agent is transitorally transformed into a rigid incom- References Cited pressible form which prevents buckling and crushing of the casing. Upon dimination of the stress the agent UNITED STATES PATENTS returns to a fluidic form which may drain or otherwise 2,707,436 5/1955 McCool ..166/299 fugitively depart from the casing providing open com- 2,965,172 12/1960 Da Roza ..l66/308 munication therethrough. 3,303,881 2/1967 Dixon ..l66/247 3,404,919 10/1968 Dixon ..l66/247 9 Claims, 5 Drawing Figures PAIENTED I97? 3.707.188

sum 1 or 4 19 Il t3 INVENTOR. Richard A. Heckman BY m aw ATTORNEY.

PATENTED HEB 26 I97? 3. 707, 1 88 sum 2 or 4 1 N VEN TOR.

Rich ard A. Heckman ATTORNEY.

PATENTED U325 I973 3.707.188

SHEET 3 OF 4 DILATANCY PLASTICITY 2 PSEUDO-PLASTICITY TRUE VISCOSITY STRESS STRESS= p. STRAIN STRAIN TRUE PSEUDO-PLASTICITY, VISCOSITY 'PLASTICITY IDILATANT STRAIN F I g. 3 INVENTOR.

Richard AHeckman BY ATTORNEY.

RATE OF FALL INJSEC PATENTED I973 3.707.188

SHEET ll- BF 4 50-50-25 MIX F6 RUN No.4 FRESH x RUN "0.4x 24HRS. STAND TIME 3/16" :1 RUN NOZ'CONCRETE MIXER FRESH RUN No.7 FRESH L3 RUN No.8 1/8" 4HOLE msc A O/A/ n 1 5/ 4 4 y x----""" x/ 88W): 0 1 I 1 l O 1 2 3 4 5 6 WEIGHT GRAMS 10' Fig. 5

INVENTOR. Richard A. Heckman ATTORNEX NON COLLAPSE STEMMING OF CASING SUBJECTED TO EXPLOSIVE EFFECTS BACKGROUND OF THE INVENTION Domestic gas consumption has increased to the point that production from reservoirs that may be produced by conventional means can no longer supply the demand. However, very large quantities of natural gas exist in very large and very thick reservoir formations in which the permeability is often too low to permit economical recovery by methods generally utilized in conventional practice.

Nuclear explosive fracturing procedures generally involving emplacement and detonation of single nuclear explosive devices have been employed and others have been proposed for stimulating production of hydrocarbons including natural gas from such tight petroliferous formations. Moreover, a procedure is disclosed in the copending application of Milo D. Nordyke, Ser. No. 89,889(70), filed Nov. 16, 1970, now U.S. Pat. No. 3,688,843 issued Sept. 5, 1972, relating to use of a vertically spaced array of nuclear explosives which are detonated either sequentially or simultaneously to more effectively fracture and interconnect various productive strata which exist in such relatively thick low permeability rock formations. Often as disclosed by said Milo D. Nordyke and otherwise as known in the art the productive formation intervals may be separated by barren strata of substantial thicknesses. These intervening strata require use of additional nuclear explosives in excess of that required to produce the fracturing effects needed to stimulate production or to require some other means such as non-collapsible casing to establish or assure communication between the successive cavity-chimney-fracture zone patterns created by the respective nuclear detonations. in other instances it may be desired to prevent communication of such pattern with certain formations, e.g., aquifers. A system which prevents collapse of a casing in a formation in proximity to a nuclear detonation is disclosed in my copending application Ser. No. 32,678(70) filed Apr. 28, 1970 now U.S. Pat. No. 3,627,041 issued Dec. 14, 1971, for Gas Recovery System. in such system steel ball packing is used to avoid collapse of the well casing and permit gas flow therethrough from a lower perforated casing portion. A description of an isotope recovery system utilizing a dilatant" fluid of unspecified nature in a product recovery conduit is disclosed in a Report No. UCRL-7963 authored by myself, entitled Isotope Production with Nuclear Explosives dated July 16, 1964.

A need therefore exists for means for establishing and maintaining gas flow communication between nuclear chimneys created in separated formation inter vals and otherwise as needed for use of nuclear chimneys for various utilitarian purposes.

SUMMARY OF THE INVENTION The invention relates generally to procedures utilzing nuclear explosives to form nuclear chimneys with an associated fracture pattern in a subterranean geological formation and, more particularly, to a procedure for establishing fluid and gas flow communication between nuclear chimneys created in geological formations separated by an impervious formation interval utilizing a tubular casing stemmed with a fugitive dilatant agent to prevent collapse thereof.

In practicing the procedure of the invention a borehole is drilled in a manner similar to those used in conventional oil and gas-well drilling and as employed in various proposed or effectuated nuclear explosive gas stimulation operations, i.e., Projects Gasbuggy and Rulison. At least the portion of the borehole situated between shot points of the various nuclear explosives which are used are cased, e.g., with steel tubing. The aforesaid tubular casing may traverse a barren strata disposed between two separated potentially productive intervals of the formation in which the nuclear explosives are to be emplaced, the tubing may traverse a for mation to which communication may not be desired or the tubing may traverse any other length of the borehole in which collapse is to be averted. Other portions of the borehole may also be cased as in usual production practice, e.g., at least at the upper end to provide for attachment of outlet control and production facilities.

Nuclear explosive devices are then emplaced at the aforesaid shot points by means known in the art. Preferably the various nuclear explosives are arranged along a cable with included firing cable, i.e., as a string and are lowered simultaneously to the shot points. For the purposes of the invention a seal means may be associated with the aforesaid string of emplacement components at a selected location above a lower explosive device so that when the devices are properly positioned the casing is sealed and retains the dilatant fluid away from the immediate vicinity of the nuclear explosive. Thenceforth, a fluidic agent having dilatant properties is introduced into said casing above said seal to stem the casing at least along a selected length in which collapse is to be prevented. Upper portions of the borehole or emplacement casing may then be stemmed in accord with conventional practice or by using a dilatant fluidic agent. Thereafter the nuclear explosive devices are detonated simultaneously. By virtue of the properties of said dilatant stemming agent collapse or buckling of the tubular casing is prevented.

The stemming agent is compounded in such a fashion that it may drain or be ejected once the detonation collapsing forces have terminated. Fluidic agents, described more fully hereinafter, provide the requisite dilatancy and drainage properties. More specifically, the seal at the lower end of the casing may be disposed within the volume vaporized by the explosive, or in the chimney region thereabove so that the rupture disk or packer seal is destroyed or opened by explosion effects so that the dilatant agent drains from the casing.

Accordingly, it is an object of the invention to provide a nuclear blasting procedure utilizing a fugitive stemming agent to prevent collapse of tubular casing subjected to nuclear explosion shock forces in a subterranean formation.

Another object of the invention is to utilize a fluidic dilatant stemming agent in a tubular casing disposed in proximity to or between simultaneously fired nuclear explosives to prevent collapse of said casing.

Still another object of the invention is to provide a nuclear blasting procedure in which a fugitive dilatant stemming agent is used to prevent collapse of casing disposed between shot points in separated strata in a petroliferous formation and in which the agent drains from the casing to establish communication between said strata. v

Other objects and advantageous features of the invention will be apparent in the following description taken with the accompanying drawings, of which:

FIG. 1 is a vertical cross sectional view of a typical petroliferous formation illustrating emplacement of nuclear explosives in the procedure of the invention;

FIG. 2 illustrates the formation of FIG. 1 following detonation of the nuclear devices;

FIG. 3 graphically illustrates the variation in viscosity values with changes in the rate of shear for materials exhibiting true viscosity, pseudo-plasticity, plasticity and dilatancy;

FIG. 4 graphically illustrates the variation in shear stress per unit area with changes in rate of shear for materials having properties corresponding to FIG. 1; and

FIG. 5 illustrates variations in relative viscosity effects related to different preparation and storage conditions.

DETAILED DESCRIPTION For purposes of illustration reference will be made to operation conducted in the Green River formation which is substantially equivalent to those in the Uinta, Piceance and San Juan basins in the Rocky Mountains and other basins generally as discussed in the aforesaid Nordyke application. More particularly, formation intervals of thicknesses and low permeability suitable for use of a spaced array of explosives from a few thousand feet to at least 15,000 feet deep exist in such formations. Such a formation as illustrated in FIGS. 1 and 2 of the drawing includes an upper impervious barren interval ll of siltstone, sandstone, or other sedimentary bed portions. An interval 122 containing low-permeability lenses 13 or other layers of rock containing petroleum hydrocarbons such as natural gas distributed in poorly connected pores is situated below interval 11. lmpervious clay or other layers 14 may be situated between lenses 13. A second interval 12b similar to interval 12a may lie below interval 12a, separated therefrom by a barren zone 16. A barren zone 17 with other successive potentially productive zones (not shown) may lie below interval 12b.

For emplacing nuclear devices to stimulate production from intervals 12a, 12b, et seq., if desired, a borehole is drilled to intersect the respective potentially productive intervals. The borehole is provided with a tubular steel casing 18 cemented in place as in usual practice and extending at least along interval 11 for purposes of the invention but may extend the length of the borehole. The upper end of casing 18 may be equipped with a valving and flow regulating facility 19, e.g., a Christmas Tree facility similar to those of conventional petroleum producing practice.

First and second nuclear explosive devices, arranged in emplacement canisters 21, 22, respectively, may then be suspended in spaced relation along a cable arrangement 23 and lowered into casing 18 so that the nuclear explosives are disposed at shot points a and [7 within midportions of or in proximity to lower portions of intervals 12a, 12b, respectively. The cable 23 may incorporate or be associated with a firing cable for detonating the explosives. For purposes of the invention, in the event that casing 18 is not extended beyond the upper shot point a, an equivalent tubular casing segment 26 is emplaced in said borehole to traverse barren zone 16. A displaceable packer or rupture seal arrangement 27 is emplaced, for example, by attachment to cable 23 at a selected location above canister 21, 'so as to be disposed in casing 18, if used, above canister 22, or in proximity to the bottom of the aforesaid casing segment 26. The packer or seal 27 may be located generally in proximity to the lower margin of zone 16 but may be located somewhat lower insofar as practicability of operation is concerned, e.g., as low as to be within the expected vaporization zone produced by the detonation.

I Inthe event that a casing segment 26 is used the upper. portion may terminate in proximity to canister 22, i.e., within the vaporization zone so that effective communication with the detonation cavity-chimney re gion is obtained. Portions of casing 18 or segment 26, if used, below canister 22 may be perforated (not shown) to provide communication with the open fracture zone created by the detonation at shot point a. Casing segment 26 or an equivalent portion of casing 18 if disposed likewise, is then filled with a fluidic dilatant anti-collapse stemming agent 28, the composition and properties of which agent are disclosed more fully hereinafter. The casing is generally filled up to a level within the anticipated vaporization zone at shot point a. Portions of casing 18 within formation interval 11 may then be stemmed with drillable concrete plugs 28, or equivalently with removable packers or with other means known in the art. Moreover, the' arrangement disclosed above may also be utilized in the lower portion of casing 18 above canister 22 with other stemming used thereabove.

The nuclear explosives are then detonated simultaneously by a triggering pulse applied to the firing cable from a conventional surface facility (not shown) with the results shown in FIG. 2. The detonation in each case first vaporizes about 50400 tons of rock per kiloton of yield. The vapor expands forming a cavity, the lower hemi-sphe'rical remnant portion 29 of which is shown in FIG. 2. The roof of the cavity collapses progressively forming a generally cylindrical chimney portion 31 after time periods of several minutes to several days and the collapsed material forms a rubble zone 32 in the chimney and cavity. Lowermost portions of the cavity may include rubble intermixed with molten formation material. The explosion creates a zone of crushed material extending outwardly from the cavity of which hemi-spheroidal portions 33a, 33b, respectively, remain. The chimney and cavity at each shot point are surrounded by a fractured zone 34a, 34b, respectively, which provide a great increase in formation permeability as well as a dramatic increase in effective well radius which provide for a highly stimulated flow of fluid or gaseous hydrocarbons into the respective chimneys.

The casing sections disposed in intervals 11 and 16 are subjected to strong axial forces as well as to shock wave and compressive forces during the explosion. These forces which may reach magnitudes of several hundred kilobars near the cavity decrease outwardly therefrom. In the interval between the shot points shock waves may be reflected back and forth several times with decreasing intensity and in interacting patterns applying severe forces to the casing. At about 1.1 cavity radii from a detonation point, the stresses in a casing extending away from a cavity, e.g., in formation 11, the stresses decrease to a level which may be withstood with typical casing and dilatant stemming need be extended no further. However, for the casing disposed between the shot points the opposing gas acceleration forces and interacting shock stresses may reach higher levels which may be effective at any point therealong to collapse or buckle the casing. In this instance it is best that the dilatant stemming agent extend the total length of the interval to be protected. When subjected to stress in the manner described, the stemming agent is transformed from a fluid relatively mobile state to a rigid relatively incompressible state which reinforces and stiffens the casing and thereby prevents buckling or collapse thereof during the explosion. While in the nonfluid state, the rupture disk or packer 27 is destroyed in the vaporization zone or is displaced byshock forces leaving the lower casing end open. Thenceforth, as the explosive forces subside, the dilatant agent returns to a fluid state and drains or is ejected, e.g., by cavity gas pressures leaving the casing openly communicating the respective chimney-fracture zones.

More specifically, in usual operating practice the upper end of the tubular casing segment 26 is disposed within the zone having a radius R,. expected to be vaporized by the device and which is equivalent to the radius R, of the cavity. Such radius may be determined by the following relation:

where R, is in meters, W is the explosive yield in kilotons, p is the bulk density of the overburden,

I1 is the depth of burial in meters and C is a constant dependent on rock type being of the order of 60 for granite and hard sandstones.

R,. in feet may be determined using 350 as the value of the constant C (c.f. UCRL-50929, Aids for Estimating Effects of Underground Nuclear Explosives, T. R. Butkovich et al, Lawrence Radiation Laboratory available from Nat. Tech. Info. Center, National Bureau of Standards). It is generally believed that the fracture zone created by a nuclear detonation extends to about 2.5 R,., horizontally, 4.4 R, vertically upward and to about 2.4 R vertically downward from the shot point. The chimney may extend upwardly to about 2.0 R while the crushed zone may extend outwardly to less than about 1.0 R,.. Explosive yields ranging from about 1.0 kiloton to as much as 200 kilotons dependent on effects desired, seismic hazard limits, etc. are appropriate for fracturing operations of the character described. Moreover, upper portions of casing 26 may be per forated to provide flow through porous portions of the crushed zone 33a or fractured zone 34 to forestall blockage of the casing in the event molten or vaporized material intrudes into the casing. However, it is contemplated that the presence of the dilatant agent will usually prevent such entry. While reference has been made to disposition of a casing section 26 in a barren zone between a pair of emplaced explosives it will be appreciated that a similar disposition between any spaced pair of whatever plurality explosives are employed may be made and emplacement may also be made between explosive devices in productive formation intervals or in any other medium. Moreover, the arrangement may also be used in a casing leading away from a single emplaced explosive, e.g., lower portions of casing 18 in formation interval 11. The spacing of the explosives may range from distances where the" fractured zones 34a, 34b may intersect to as great a distance as desired.

To provide for hydrocarbon production from the aforesaid intercommunicated well complex, the stemming in the upper portion of the casing is removed by drilling or otherwise as appropriate. Hydrocarbons flowing into the lower chimney may then flow upwardly through intact noncollapsed casing section 26 to mix with hydrocarbon flowing therein from interval 12a and be withdrawn therewith through facility 19 for dis tribution or use.

Fluidic dilatant materials including the stemming agent of the invention are characterized by certain viscosity properties illustrated by curves, 1, in FIGS. 3 and 4 of the drawing. More particularly, as the rate of shear strain, shown by curve 1, FIG. 3, is increased in a dilatant the viscosity increases as a curved function for low rates of shear but varying at a very rapidly increasing rate to approach infinity. That is, the fluid congeals to a rigid non-fluid form, shown by curve, 1, FIG. IV, which reverts to a fluid form when the shear stress is removed. These effects are in contrast to the behavior fluids exhibiting, plasticity, pseudo-plasticity and true viscosity illustrated by curves 2, 3, and 4, of FIGS. 3 and 4, respectively.

Dilatant materials generally comprise a liquid phase having a discrete particulate phase dispersed therein. The liquid phase or vehicle may comprise water, a hydrocarbon, a silicone fluid or other liquid having suitable properties. For lower temperatures, i.e., below the boiling point of water, water may be employed as being more economical. For higher temperatures, e.g., up to several hundred degrees centigrade which may be encountered at depth in typical nuclear fracturing operations, tricresyl phosphate and tetralin or petroleum hydrocarbon fractions such as diesel oil, stove oil, kerosine and naphthenic oil fractions may be used. Generally speaking a material which has low lubricity and low film strength is believed preferable. The particle phase may comprise an organic material such as starch which can be dispersed, for example, in a water based vehicle. When using water as a vehicle it is found advantageous to include a deflocculant such as a guar gum preparation or other equivalent agent. Other materials suitable for the particle phase include finely divided silica and silicate materials such as various colloidal silicas, e.g., quartz powder, of l-l 0 microns, and other finely-divided silica materials. Painters smaltz, i.e., spherical glass particles of about 25 microns diameter may be used as may carbon black and certain other fillers and reinforcing agents used in rubber and lOfiOll R plastic compounding. Generally speaking sufficient vehicle is employed to at least till the interstices between solid particles or to provide a dispersion.

Amounts in the range of about 20 to about 80 percent by weight are representative. Deflocculant agents may comprise very small proportions, i.e., about 0.1 to 1.0 percent if particularly effective, e.g., guar gum while up to about 10 percent of less effective agents may be needed. The remainder of the composition, i.e., about 20 to 80 percent may comprise the particulate phase. It will be appreciated that the effect of relative proportions of the agents on the viscosity are interrelated and that the proportions may be varied and selected by employing viscosimetric measurements. It may be noted that the initial viscosity should be in the approximate range of 2070 poises with a preferred range of about 4555 poises in order that the agent will flow to fill the casing. With dilatant agents pumping is often difficult since most pumping devices develop at least sufficient localized shear to cause the agent to congeal and therefor to freeze the pump. However, with the lower shear rate developed in pouring the agent may be flowed down the casing and fill it to the desired height.

Further details as to the preparation and positioning of a dilatant stemming agent are set forth in the following illustrative example.

EXAMPLE The recipe and procedure used herein are based on the dilatant fluid stemming of 500 feet of 14 inch schedule 30 pipe casing.

I. TOTAL MATERIALS REQUIRED A. Finely powdered corn starch.

1. 18,000 pounds in IOOpound bags.

B. Clean water.

1.2150 gallons. C. Vegetable gel: Guar gum gel (Jaguar 315 C M or equivalent) 1. 90 pounds. D. Formaldehyde. l. 2.0 gallons.

II. RATIO A. Equal weights of starch and water.

B. Gel: 0.5 percent (wt. starch).

C. Formaldehyde: 0.1 percent (vol. water).

Ill. SUGGESTED MIXING PROCEDURE FOR 5 YD AMOUNTS A. Amounts:

l. 5100 pounds starch.

2. 612 gallons H 0.

3. 25.5 pounds gel.

4. 0.60 gallons formaldehyde (preservative) B. Procedure:

1. Fill cement mixing truck or equivalent mixer with 550 gallons water. 2. Rotate at rpm. 3. Add 5100 pounds starch from containers through a V2 to l-inch screen to remove lumps. Add 25.5 pounds gel periodically with starch addition. Add 0.60 gallons formaldehyde last. Rotate for /2 hour at 10 rpm. Wash bin sides down with 62 gallons of water. Rotate for an additional 5 to 10 minutes. The final mixture should be fairly smooth.

l0. Pour or flow slowly into pipe.

11. Repeat steps 1 to 10 until pipe is filled to desired level.

12. Liquid mix can be stored from 3 to 4 days. However, it is best to use as soon as possible to minimize time for material separation. The material tends to setup somewhat on storage, e.g., 24 hours or more which, in situ, does not affect results.

For compounding use a practical viscosimeter was devised and employed. Such viscosimeter comprised a 5 to 6 inch l.D. tubular cylinder in which the agent was disposed. A thin 4 inch diameter steel plate, e.g., l/8 to 3/16 inch in thickness having either four 1/8 inch or 3/16 inch diameter evenly spaced holes on about a 3 inch diameter circle was used as the moving element. Various weight was placed on the plate and the rate of fall in inches/second was measured. Data obtained on an agent comprising 50 parts by weight starch, 50 parts water and 0.25 parts guar gel solution under various mixing and storage conditions are illustrated in FIG. 5. The typical curving of fresh dilatant agents in curves 2, 7 and 8 while a settingtendency is noted in comparing curves 4 and 4x. The latter effect does not disturb the results and may be related to the mechanism whereby the gum prevents starch separation (flocculation). It is thought that the indicated effect may be due to hydrogen bonding and that the latter may also be involved in the relative rigid solution structure produced by rapid shear.

While there has been described in the foregoing what may be considered to be preferred embodiments of the invention, modifications may be made therein without departing from the teachings of the invention and it is intended to cover all such as fall within the scope of the appended claims.

What I claim is: 1. In a process utilizing nuclear explosives for fracturing a subterranean geological formation, the steps comprising:

drilling a well bore to intersect the interval of said formation which is to be fractured;

disposing an elongated section of tubular well casing in the well bore between an upper and a lower shot point location within said formation interval and grouting said casing in place;

emplacing nuclear explosive devices at said upper and lower shot point locations and disposing a dis placeable seal means at the lower end of said casing section;

disposing a dilatant fluid stemming agent in said casing section; stemming the well bore above said upper shot point location;

simultaneously detonating said nuclear explosive devices to produce nuclear explosion cavities and chimneys surrounded by fracture zones, said dilatant stemming agent preventing collapse and buckling of the casing during the explosion, said seal means being displaced by explosion effects so that the dilatant stemming agent drains from the casing subsequent to the explosion and thereafter said casing section provides communication between the respective cavity-chimney-fracture zone systems at said shot points.

2. A process as defined in claim 1 wherein said formation interval is in a petroliferous formation, wherein said shot points are in gaseous or fluidic hydrocarbon bearing strata and said casing is disposed in barren strata situated between said shot points so that flow of said hydrocarbon from said strata is stimulated and flow thereof between said respective cavity-chimney fracture zone systems through said casing occurs.

3. A process as defined in claim 2 wherein said dilatant agent comprises a liquid vehicle and a dispersed particle phase.

4. A process as defined in claim 2, wherein portions of said well bore above said upper shot point is also provided with a tubular casing, wherein the aforesaid casing is also sealed at the lower end with a displaceable seal means and wherein the aforesaid casing is also filled with fluidic dilatant stemming agent, so as to provide communication to the upper cavity-chimney fracture zone system.

5. A process as defined in claim 3 wherein said vehicle is a liquidic material selected from the group consisting of water, hydrocarbon, silicane, tricresyl phosphate and tetralin.

6. A process as defined in claim 5 wherein said dispersed particle phase is a particulate form of a meterial selected from the group consisting of starch, silica, insoluble silicates, glass and carbon black.

7. A process as defined in claim 6 wherein said vehicle comprises water, said particle phase comprises starch and a vegetable gum deflocculant is included.

8. A process as defined in claim 7 wherein said dilatant agent comprises about 50 parts by weight of water, about 50 parts by weight of starch and about 0.25 parts by weight of guar gel.

9. A process as defined in claim 4 wherein the upper and lower ends of said tubular well casing section between said upper and lower shot points is disposed within the expected vaporization zone of the nuclear devices emplaced proximate thereto and wherein the lower end of the casing above the upper shot point is disposed within the vaporization zone of the upper nuclear explosive.

lObOl 2 

2. A process as defined in claim 1 wherein said formation interval is in a petroliferous formation, wherein said shot points are in gaseous or fluidic hydRocarbon bearing strata and said casing is disposed in barren strata situated between said shot points so that flow of said hydrocarbon from said strata is stimulated and flow thereof between said respective cavity-chimney-fracture zone systems through said casing occurs.
 3. A process as defined in claim 2 wherein said dilatant agent comprises a liquid vehicle and a dispersed particle phase.
 4. A process as defined in claim 2, wherein portions of said well bore above said upper shot point is also provided with a tubular casing, wherein the aforesaid casing is also sealed at the lower end with a displaceable seal means and wherein the aforesaid casing is also filled with fluidic dilatant stemming agent, so as to provide communication to the upper cavity-chimney fracture zone system.
 5. A process as defined in claim 3 wherein said vehicle is a liquidic material selected from the group consisting of water, hydrocarbon, silicane, tricresyl phosphate and tetralin.
 6. A process as defined in claim 5 wherein said dispersed particle phase is a particulate form of a meterial selected from the group consisting of starch, silica, insoluble silicates, glass and carbon black.
 7. A process as defined in claim 6 wherein said vehicle comprises water, said particle phase comprises starch and a vegetable gum deflocculant is included.
 8. A process as defined in claim 7 wherein said dilatant agent comprises about 50 parts by weight of water, about 50 parts by weight of starch and about 0.25 parts by weight of guar gel.
 9. A process as defined in claim 4 wherein the upper and lower ends of said tubular well casing section between said upper and lower shot points is disposed within the expected vaporization zone of the nuclear devices emplaced proximate thereto and wherein the lower end of the casing above the upper shot point is disposed within the vaporization zone of the upper nuclear explosive. 